rekrunner wrote:
Did Paula race marathons and semi-marathons on a bike? Did you see these publications?
Schumacher et al, "Diurnal and exercise-related variability of haemoglobin and reticulocytes in athletes", In J Sports Med 2010;31;225-30
"The most relevant confounder is physical exercise, which significantly increased Hb. This increase can be explained by exercise induced plasma volume concentration. Many previous investigations have highlighted this issue. The data of our investigation demonstrates that Hb returns to values around pre-exercise baseline within approximately 2h after the cessation of physical activity"
This is why we have a two hour rule.
The effect of physical activity/training was +0.459 g/dl, this is compared against a baseline of 14.84 g/dl. Unfortunately they don't don't split the 'physical activity effect' into endurance (END) vs non-endurance (NON-END) vs control (CON), they are all lumped together. Despite this you can see the overall effect to Hb levels is only +3%; statistically significant? Yes, but they used a t-test when they should have at the least used an ANOVA with a post-hoc analysis like Dunnets. I suspect the differences are likely to be negligible if not negative for endurance athletes.
Some other snippets from the article.
"In our investigation, END show lower Hb than NON-END or CON.
As for the exercise induced changes described above, this phenomenon is due to the expanded plasma volume following regular endurance exercise. It is well known that endurance athletes display lower concentration based variables such as Hb."
"The amount of fluid intake had no measurable impact on Hb in the investigated subjects ( â—â–¶ Table 3 ). Although this is surprising at first sight, there is scientific evidence suggesting that plasma volume remains constant or even increases at first despite mild degrees of exercise- or temperature induced dehydration... (several cyclists participating in the study performed 6 h training rides during summer with several long climbs)."
"In our investigation, several preanalytical conditions of sampling were not standardised to accurately mimic the conditions encountered in the field. International guidelines for laboratory medicine and most standards of procedure for blood sampling in doping control suggest to take venous blood samples early in the morning in a fasted stated after 15 min in a seated position. Tourniquet time should not exceed 60 sec. Despite these deliberately chosen limitations of preanalytical conditions in the current study, the intra-individual CV for our physically active athletes was still comparable to the data reported in the literature for the control- and endurance trained groups. This CV includes the analytical and biological variability"
This last quote is interesting because here they admit to not following the standard guidelines for sampling and yet it had no effect on the individual variability (CV is coefficient of variation).
Why was this study performed?
"Most sporting federations perform blood tests in the morning and without prior exercise. It has been reported however that unscrupulous athletes
take advantage of this time schedule by using blood manipulations such as transfusions after the blood tests have been performed in the morning, knowing they will not be tested afterwards."
They wanted to understand the diurnal variability on hemoglobin in athletes so that when someone like Paula presents with a 20% gain in Hb levels pre to post race, they can rule out all sources of variation and conclude that a blood transfusion has taken place. According to this article, Hb levels decrease throughout the day as plasma volume returns from nocturnal dehydration, and that decrease is only 3.5%. Mind you, that decrease is still greater than the increase from physical exercise/training...
Overall, it's a poorly analysed piece of work published in a low impact journal (IF 2), so I would take any of the conclusions with a pinch of salt.